Problem: Simplify the following expression: $p = \dfrac{-9}{9n} - \dfrac{-6}{9n}$
Solution: Since the expressions have the same denominator we simply combine the numerators: $p = \dfrac{-9 - (-6)}{9n}$ Combine like terms: $p = \dfrac{-3}{9n}$ Simplify by dividing numerator and denominator by 3: $p = \dfrac{-1}{3n}$